Vaccination information
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Pfizer and BioNTech's COVID-19 vaccine is based on messenger RNA, or mRNA, which helps the body generate immunity against the coronavirus, specifically the SARS-CoV-2 virus. The idea is that the synthetic mRNA gives the body instructions for making proteins found on the surface of the virus. Once produced in the body, these proteins (or antigens) stimulate the immune system's response, potentially resulting in protection for the individual who received the vaccine.
The results of phase 3 studies, involving more than 44,000 volunteers and already published in a qualified scientific journal, showed that the overall effectiveness of the vaccine against COVID-19 was 95%, with a two-dose schedule, within a 21-day interval between doses. The data also showed that the vaccine was well tolerated, with no serious safety concerns noted.
The vaccine can be stored at -90°C to -60°C for up to 6 months, at -25°C to -15°C for a single period of 2 weeks and in a refrigerator temperature at 2°C to 8°C for up to 31 days. To enable transport to different countries or application sites, Pfizer has developed a package with the potential to store the vaccine at the required temperature on the basis of dry ice. In this package, the vaccine vials can be kept for up to 30 days, as long as the correct maintenance of dry ice is carried out.
Johnson & Johnson 's vaccine is a "viral vector vaccine." To create it, the drugmaker's researchers used a harmless adenovirus – the viral vector – and exchanged a small part of its genetic instructions with the genes for the “spike” protein of SARS-CoV-2. When this modified adenovirus is injected into a person's arm, it enters their cells. Afterwards, the cells “read” the genetic instructions necessary to produce the protein, and the vaccinated cells start to present this very protein on their surface. Thus, the person's immune system will recognize this type of protein, through which the coronavirus penetrates into human cells, creating antibodies against the virus. Viral vector vaccines are safe as adenovirus cannot replicate in human cells or cause disease – the spike protein of SARS-CoV-2 cannot trigger Covid-19 without the rest of the coronavirus.
According to the US Drug Authority (FDA) analysis, the Johnson & Johnson vaccine was 72% effective in preventing all types of Covid-19 infections, and 86% effective in preventing severe cases of the disease – so, while there is still some probability that a person could become infected, the chances of someone being hospitalized or dying from Covid-19 after being vaccinated are significantly low.
Unlike all vaccines available in Portugal so far - from companies such as AstraZeneca, BioNTech-Pfizer and Moderna - whose immunization requires two doses with a certain interval of days between them, the Johnson & Johnson vaccine requires only one dose .
Moderna, a Massachusetts-based vaccine development company, has partnered with the National Institutes of Health to develop and test a coronavirus vaccine known as mRNA-1273.
This is a messenger mRNA-type vaccine and for that reason it contains mRNA with instructions for the production of the causative protein of Covid-19, the S protein of "Spike" that belongs to the surface of the Sars-Cov-2 virus and is used for its entry into the body's cells. In addition to mRNA contains the following ingredients: Tromethamine, Acetic Acid, Tromethamine Hydrochloride, Sodium Acetate, Sucrose and Lipids. When administered, the cells will read the mRNA, temporarily producing the S protein that will be recognized by the immune system as foreign, leading to the production of antibodies, with the activation of T cells for subsequent attack. This production of antibodies means that when a person comes into contact with the virus in question, he does not develop the disease, since his body already has all the necessary tools to defend itself.
RNA is a very fragile particle, which would be cut into pieces by natural enzymes if injected directly into the body. To protect the vaccine, Moderna wraps the mRNA in oil bubbles made of lipid nanoparticles.
It is also due to its fragility that the Moderna vaccine cannot be stored at room temperature, having to be refrigerated at -4°F (-20°C) when being shipped and stored, and should be stable for up to six months.
This vaccine requires two injections, given 28 days apart, to prepare the immune system well enough to fight the coronavirus. But it's still recent, researchers don't know how long its protection can last.
The Modern vaccine has the great advantage of having a high efficacy against Covid-19, around 94.1%, but it can only be administered to people aged 18 years or over.
As with any medicine, vaccines can also trigger unwanted effects. The most common of this during clinical trials was generally mild or moderate and improved a few days after vaccination. These included pain and swelling at the injection site, tiredness, chills, fever, swollen and tender lymph nodes under the arm, headache, muscle and joint pain, nausea and vomiting, affecting more than 1 in 10 people. . Redness, hives, and skin rash at the injection site and the body in general also occurred in less than 1 in 10 people. Itching at the injection site has also been seen in less than 1 in 100 people and rarely in less than 1 in 1000 people, swelling of the face, which can affect people who have previously received facial injections for cosmetic purposes, and weakness in the muscles on one side of the face (acute peripheral facial palsy or paralysis). Allergic reactions have also developed in people who have received the vaccine, including a very small number of severe allergic reactions (anaphylaxis).
The vaccine, called AZD1222, was developed by a team at Oxford University and the British-Swedish pharmaceutical company AstraZeneca. The research team includes scientists from the Jenner Institute and the Oxford Vaccine Group.
It is a vector vaccine. According to Fiocruz, it was developed with chimpanzee adenovirus non-replicating vector technology, harmless to humans. It is a weaker version of the flu virus common in chimpanzees and also contains proteins contained in the genetic material of the Sars-Cov-2 virus.
After vaccination, adenovirus enters a few cells in the human body. These cells use the gene to produce the Spike protein. The immune system then recognizes this as foreign and, in response, produces antibodies and T cells, which ideally protect against infection with the Sars-CoV-2 coronavirus.
AstraZeneca had to slightly downgrade the data on the effectiveness of its immunizer: it protects by 76%, instead of 79%, against infections with the new coronavirus that show symptoms, reported the Swedish-British drugmaker on its website at 25 of March 2021. This means that in a group of vaccinated individuals there were 76% fewer cases of disease than in the control group that received a placebo. Among those over 65, the rate is much higher, reaching 85%. And the vaccine protects 100% against a serious clinical condition.
Earlier, the US National Institute of Allergy and Infectious Diseases (NIAID), headed by epidemiologist Anthony Fauci, had voiced doubts about the effectiveness of the AstraZeneca vaccine: "obsolete information" would have "communicated an incomplete picture of effectiveness." In reaction, the Swedish-British company released new data, after conducting tests with 32,449 participants, of which a third were vaccinated. Previous studies have indicated that effectiveness could reach 82% or even 84% if a second dose is given within 12 weeks or more.
AstraZeneca's product data is also good when it comes to hospitalizations. A study by the University of Edinburgh showed that four weeks after the first dose the risk of having to be hospitalized due to covid-19 dropped 94%. For the Biotech-Pfizer vaccine, the registered drop was 85%.
The European Medicines Agency stated on April 7, 2021 that there is a possible link between the use of the Oxford vaccine, manufactured by the company AstraZeneca, and the formation of blood clots. The EMA noted, however, that these cases are very rare, and the benefits offered by the vaccine far outweigh the risks of side effects. The EMA recommended that blood clot formation be included as a very rare side effect of the vaccine.
The agency said health professionals and people who are vaccinated should be aware that there is a possibility of very rare cases of blood clots in combination with low blood platelets, and added that the majority of reported cases occurred in women under 60 years within two weeks of vaccination. Even so, the agency said it was unable to identify possible risk factors, such as age or gender, based on the information currently available. Shortly after the European agency's statement, the World Health Organization (WHO) vaccine safety advisory panel said the link between the AstraZeneca vaccine and the rare cases of blood clots is "considered plausible but has not been confirmed". A group of independent experts reviewed the latest global data and stated that specialist studies would be needed to fully understand the potential relationship between the AstraZeneca vaccine and possible risk factors. "It is important to note that, while worrisome, the events under evaluation are very rare, with low numbers of reported cases among the nearly 200 million individuals who have received AstraZeneca's covid-19 vaccine worldwide," experts said. .